VEGGIES: Heat oil & butter in a large pot (or 6-quart dutch oven) over medium heat. Add mirepoix and cook until softened, about 8-10 minutes. Press to edges of pot.
BEEF: Increase heat to high, add beef to the center of the pot, sear, then break it up and cook until browned, about 5 minutes.
DEGLAZE: Pour in red wine (or broth/water) and cook until most of the liquid evaporates.
ADD FLAVOR: Stir in tomato paste and garlic, sauté for 2 minutes. Add crushed tomatoes and cook, stirring constantly, for another 1 minute.
ADD EVERYTHING ELSE: Stir in Worcestershire sauce, bay leaves, seasonings, and cream. If serving immediately, stop here. If simmering, add 1-1/2 cups hot water.
TO SIMMER: Swap pot to smallest burner. Cover and cook on lowest heat for at least 1-1/2 hours up to 3 hours. Stir occasionally and add more water (1/2 cup at a time) IF needed to prevent the sauce from sticking. OR transfer everything to a slowcooker and cook on low for 5-6 hours.
FINISH: When sauce has thickened to the consistency of sloppy joes, it's ready! Adjust seasoning if needed; I typically add 1/2 tsp salt. Add sugar and balsamic vinegar to balance flavors.
PASTA: Cook spaghetti according to package instructions. Don't forget to salt the water (I add 1 tbsp salt to 12 cups water). Reserve 1-1/2 cups of pasta water before draining.
OPTIONAL: EMULSIFY: Add cooked pasta directly into bolognese sauce and use tongs to toss until pasta is well coated. Add reserved pasta water as needed to loosen the sauce.
ENJOY: Grate fresh Parmesan on top, add fresh parsley, and enjoy!
Notes
Note 1: It's crucial to finely dice these veggies so they integrate nicely into the sauce. You can use a food processor if you prefer. I typically use about 1-1/4 cup onion, 3/4 cup celery, and 3/4 cup carrots, which is equivalent to 1 large onion, 2-3 celery stalks, and 2-3 carrots.MAKE AHEAD: The sauce gets better overnight! Cool completely, then refrigerate. Warm it on low heat before adding pasta. It can be frozen for 3 months or kept in the fridge for 3-4 days. Once tossed with pasta, it's best eaten within 3 days, but fresh pasta is always the tastiest!